docs: def get_required_permissions(self, request):
          """ Returns the required permissions to access the considered object. """
          perms = []
  
          if not self.permission_required:
              return perms
  
          if isinstance(self.permission_required, string_types):
              perms = [self.permission_required, ]
          elif isinstance(self.permission_required, Iterable):
              perms = [perm for perm in self.permission_required]
          else:
              raise ImproperlyConfigured(
                  '\'PermissionRequiredMixin\' requires \'permission_required\' '
                  'attribute to be set to \'<app_label>.<permission codename>\' but is set to {} '
                  'instead'.format(self.permission_required)
              )
          return perms